In the use of machine tools, welding operations, painting operations, and some chemical processes, it frequently is necessary to provide protective shielding between the operator of the machines or equipment and the point of operation. Such shielding functions as a chip retainer, spark arrest, or splash guard during use of the machine to prevent possible injury to the machine operator. In addition, shielding assists in confining the waste products of machining to a relatively small area which facilitates clean-up.
Machine shops are most prone to potential injury, particularly to eyes, in machine operations such as metal removal in a variety of forms, such as drilling, grinding, sawing, milling, die-punching, shearing, boring and the like, and in spray-mist coolant applications and other functions. In grinding operations and welding operations, there is substantial concern about spark arrest, both for protection of the operators of such machines and to minimize the potential for the creation of fires due to sparks. In addition, high-arc flash in welding areas may cause severe eye burn, whether the individual is looking directly at the welding flash or inadvertently eyes a flash reflecting off a near wall or other structure. In such instances, a non-transparent shield, either portable or machine-mounted, is required to prevent injury.
The need for protective shielding for machines and other operations of the types mentioned above long has been known. A variety of attempted solutions have been made. From a safety standpoint, the ideal shield is a permanent one located between the machine operator and the workpiece and cutting head, grinder, or the like, of the machine. This is possible to achieve in some automated or semi-automated operations. For many applications, however, a permanently located shield is not possible or may be impractical. Also, it is frequently desirable for an operator to have direct access to the operating point of a machine for various purposes, such as changing cutting heads or checking on work progress. If permanently installed shields are located between the operator and the operating head of such a machine, it is necessary first to remove the shield before the operator can perform the desired operation or adjustment to the machine.
Consequently, movable or retractable shields have been devised for specialty applications in the past. Three patents which are directed to such protective covers or shields are the patents to Moritz, U.S. Pat. No. 4,039,021; Zettler, U.S. Pat. No. 3,824,890; and Richter, U.S. Pat. No. 3,366,012. The Moritz patent discloses a protective cover for the guiding path of machine tools. This patent utilizes a cover in the form of several rigid overlapping cover plates telescopically movable into and out of each other, and each successively decreasing in size from one end to the other end of the system. The plates are moved back and forth by two sets of pairs of retracting arms interconnecting the top and bottom edges of the plates. A number of rods, cylinders, pistons, cams, and other components are necessary to effect the shield movement. The apparatus used in Moritz is generally a pantograph-type of structure. Because of the nature of the structure, it is necessary that the protective plates are rigid plates.
The Richter and Zettler patents are somewhat similar to one another, and both disclose telescoping structures using a pantograph support member. Richter discloses a plurality of overlapping rigid plates which are used to catch chips and cutting fluid from the cutting head of a tool. The Richter device is made to extend at an angle generally vertically from an area in the tool base to a point located directly beneath the cutting head of the tool. Rigid plates are involved and each of the plates is connected to one of the segments of a pantograph. This is a fairly expensive structure and one that is complex to manufacture. The Zettler patent discloses a device in the form of a chip guard for a horizontal spindle machine tool. A pantograph bellows surrounds the top and sides of the tool operator head. Because of the necessity for pantographs located on both sides of the device, the structure is cumbersome and expensive. It also is not flexible in the vertical direction, due to the rigidity imparted by the pantograph members.
Other attempts for providing guards or shields to prevent splinters and the like from being thrown from a saw or cutting tool out into the surrounding area are disclosed in the patents to Blessinger, U.S. Pat. No. 4,096,789; Seck, U.S. Pat. No. 3,568,567; and Benuzzi, U.S. Pat. No. 4,297,928. The guard devices or shield devices disclosed in these patents all are in the form of permanently mounted, non-retractable holders from which movable or flexible guard strips are hung surrounding the tool head or operating area. In the Blessinger patent, a box-like structure is placed over the top of a saw and flexible strips are hung downwardly from the perimeter of the box above the work area. This permits workpieces to pass underneath the strips, bending or moving them accordingly as the workpieces are fed into the saw. In the Seck device, a curtain made of chain mesh hangs downwardly from a holder located above the tool head and workpiece to partially surround the machining zone to confine movement of shavings thrown off by the workpiece. The flexibility of the chain curtain permits it to accomodate itself around workpieces of different shapes. The Benuzzi patent discloses a shield in the form of longitudinal rods for supporting a plurality of slats hingedly mounted side by side for swinging movement through a pre-determined angle to accomodate workpieces of different thicknesses passing beneath the slats.
Although the Moritz, Zettler and Richter patents all are directed to collapsible shields, these devices are not inexpensive to construct and, further, do not have a wide degree of flexibility which permits their use on a variety of different types of machines or in a variety of different applications. Consequently, it is desirable to provide a retractable safety shield which is simple to construct, easy to use, and which is capable of nearly universal application to a wide variety of machines and other uses.